Various hip implant components are known. Among these are acetabular cups.
In one such cup, provided as an ensemble, an ultra high molecular weight polyethylene (UHMWPE) cup insert is positioned in a metal shell through an internally biased retaining ring on the shell that engages a corresponding annular groove on the cup insert. The cup insert may have a hood and recessed stops about a circumference of its lip for “dialing in” the hooded insert with respect to a surgically implanted shell that has corresponding upraised post stops on its rim for engaging the recessed stops of the cup insert. The shell may have a porous or mesh outer coating for bonding with bone of the surgically prepared acetabular socket of the patient.
One problem with such an ensemble revolves around the UHMWPE. Many practitioners understand UHMWPE, as useful and desirable as it is, especially in total joint prostheses, to form wear debris particles, which over the course of time after implantation may engender osteolysis and aseptic loosening of the implant.
Accordingly, metal or, even better, ceramic, is often proposed to replace the UHMWPE.
However, replacing an UHMWPE insert with ceramic is not always a simple exchange.
In another such cup, a ceramic cup, the body is provided as one piece. A roughened outer surface such as from grinding it to be rough or from adding a metal porous coating such as from metal vapor deposition may be provided to help bond the implant to the bone stock of the prepared acetabulum of the patient. In the former case bone ingrowth often insufficiently occurs, necessitating the use of surgical cement, which itself may fail over time, and in the latter case it may be desirable to avoid a sputtered metal coating on the ceramic cup because of cost and other considerations.
Another arrangement may provide a taper on an outer surface of the cup onto which a correspondingly tapered ring may be fitted. Such an arrangement is not without its drawbacks.
Nevertheless, it remains desirable to improve the instant art, noting especially the ever present desire of surgeons and their patients for better and better joint implant performance.